It's not the same.
1) If Wolfram and Hart had a sacrificial pit for kids to keep the world alive, Angel would know, and it would have been an issue, because he has a soul, but Angel never came to interfere.
2) Vengence demons, and similar demons, are free roaming multi-dimensional entities in the Buffyverse who have an investment in having people to serve, and people to torture. The Ancients destroying the world doesn't work for them, and they would attempt to interfere, probably if all else fails, involving Buffy and Willow, because Buffy is formed as the original demon repression device. Stopping the ancients would be her job, and the demons who like having people around to play with would help her. There was no sign of that, but plenty of opportunity.
3) The arrangement with the ancient ones would have been known by other mystical communities in the BuffyVerse, like the witches that trained Willow, and the old lady with the Glottal Stop. The latter is part of a group who accurately predicted millenia before everything necessary to stop a problem so dire they had to predict it millenia ago and prepare for that day over all that time. They wouldn't have missed something like the Ancients, nor neglected the danger.
4) Willow, having gone fully dark, and then in recovery, linking to the entire earth and its living systems, would have percieved and understood the existence and arrangements for the great evil. In the BuffyVerse, the great evil is the first evil. If the Ancients existed in the Buffyverse, they were under the first evil. The first evil did not arrange for the ancients to come bitch slap Buffy, she used a wingman and a bunch of old blue vampires. If the ancient's pit existed in the BuffyVerse, the first would have attracted the slayers to the cabin and used them to feed the ancients, or lured them there to let them stop the organization, resulting in the end of the world. Season 7 would have ended badly.
Nope, not the same.